


Maybe a Sister's Not So Bad

by WriteInAnonymity



Category: Supergirl (TV 2015)
Genre: Adopted Sibling Relationship, F/F, Masturbating together, Orgasm, Pseudo-Incest, Sister/Sister Incest, Sleeping Nude, Smut, Underage Masturbation, Vaginal Fingering, caught masturbating
Language: English
Status: Completed
Published: 2021-03-14
Updated: 2021-03-14
Packaged: 2021-03-22 08:41:16
Rating: Explicit
Warnings: Underage
Chapters: 1
Words: 3,013
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/30036024
Author URL: https://archiveofourown.org/users/WriteInAnonymity/pseuds/WriteInAnonymity
Summary: On her first night sharing a room with her new little sister, Alex finds out that Kryptonians like to sleep in the nude. She isn't prepared for how this makes her feel.
Relationships: Alex Danvers/Kara Danvers
Comments: 4
Kudos: 70





	Maybe a Sister's Not So Bad

Alex had always thought she was lucky, being an only child. She saw what it was like for her friends who had brothers or sisters and, from what she could tell, siblings were designed for the sole purpose of getting on each other’s nerves. Take just the other day, when her friend Angie had been forced to come to school with her messy hair shoved in a beanie because her older sister had been hogging the bathroom. At the time, Alex had been secure in the knowledge that she’d never have to deal with anything like that. In her fifteen years of life, her parents had not once even hinted at a desire for another child.

And then, earlier that day, Kara Zor-El—sorry, Kara _Danvers_ —had appeared in her life. It was like waking up one morning and finding someone had attached a ball and chain to her ankle while she was sleeping, and now she had to lug that thing around and act like it wasn’t completely ruining her life. Oh, and also, the ball and chain had alien superpowers.

Yeah, that last part was no metaphor. Alex’s new thirteen-year-old sister, who most people probably wouldn’t even spare a second glance, was a _fucking space alien_. Apparently, she would be developing all kinds of freaky abilities now that she was living on Earth. Thank God she at least looked normal. School was going to be bad enough now as it was.

“Alex? Is something wrong?”

Kara’s voice pulled Alex out of her brooding. They were in their room (she already missed the days when it was just _her_ room). Alex was lying on her bed on her stomach, notes spread out around her. She’d been trying to focus on studying while ignoring the other presence hovering in the room, but evidently she hadn’t been doing a very good job, since she’d been stuck on the same index card for the past five minutes. She looked up at Kara, who was standing so close to the bed that Alex’s nose almost bumped her, and she leaned back in surprise.

“Nope, nothing wrong here,” Alex said in a falsely cheery voice.

“Okay, good.” Kara nodded at her and gave a small smile. Then she turned around and went back to where she’d been before, standing and staring at the stars out the window.

What had that been about? Had she somehow noticed that Alex was having trouble focusing? Normally, Alex would think it was impossible, but it probably wasn’t a good idea to cling to normality when talking about an alien sister. Was mind reading one of the powers her parents had mentioned? No, if that were the case, then Kara would’ve been able to tell that Alex had been lying through her teeth.

Alex sighed. There she went, thinking about Kara again instead of her history test. She glanced at the clock and decided that it was time to give up on getting any more studying done. “I’m going to bed,” she announced.

“Okay.” Kara turned to face her again. “I will too.”

And then Kara did something that caught Alex completely by surprise: she reached down and started pulling off her pants right in front of Alex. Apparently, her panties were coming with them, because Alex caught a quick glimpse of brown hair before she turned away, face burning. “What the fuck are you _doing_?”

“I’m getting ready for bed.” Kara sounded confused by Alex’s reaction. “Do you not take off your clothes when you sleep on Earth?”

Oh God, she wasn’t just getting changed in front of her, she was going to _sleep_ like that?

Alex turned back to yell at Kara to put some clothes on, but her mouth dried up at the sight that met her. Kara was completely naked now, her clothes in a heap on the floor by her feet. Alex’s eyes went immediately to her breasts. They were smaller than her own, barely big enough to need a bra. Seeing them set off a pleasant burn deep in her stomach, and her eyes drifted downwards, stopping on the dark bush obscuring her—

Alex snapped her head up so fast that she felt her neck pop. “We wear clothes to sleep. Especially when there’s someone else in the room.” She didn’t let her vision wander from Kara’s eyes.

“Oh, sorry. I didn’t know.” Kara started leaning down to pick up her clothes.

“But I don’t mind if you sleep like that,” Alex said, her mouth moving before her brain could fully process what she was saying. “Umm, just don’t let Mom or Dad see you like that in the morning,” she added, mentally cringing at the thought.

“Thank you!” Kara smiled at her. “Do you want to try it too? I would think it’s much more comfortable than wearing clothes to bed.”

“Oh, nah, that’s fine.” Alex turned away and busied herself with gathering up her notes until she heard Kara climb into bed. Now that it was safe to turn around, she grabbed her pajamas and fled to the bathroom to get changed.

She tried to keep her mind blank as she pulled on her pajamas, did her best to ignore the fluttering feeling that was still lingering in her chest. This was normal, right? She’d just been surprised, that was all. Anyone would’ve reacted the same.

Thankfully, Kara was still under the covers when Alex got back. After saying goodnight, Alex turned off the lights and tried to get comfortable in bed.

She was usually able to drift off within minutes, but that wasn’t happening tonight. The knowledge that there was a naked girl there, just on the opposite side of the room, had her head spinning. Her mind kept flashing back to that image of Kara, to the gentle swell of her breasts, the soft curves of her body. There was a heat building up inside her. Almost of its own volition, her hand lifted up the elastic of her shorts and snaked down until it was resting directly on the burning between her thighs.

Fuck, was she really going to do this?

Alex held her breath and strained to hear over the sound of her heart pounding in her eardrums. Kara’s breathing was slow and measured. Maybe she was already asleep?

It would have to do; Alex couldn’t hold back any longer. She hadn’t even started, and already her fingers were slick with her arousal. Her mind was still on Kara as she slid her fingers between her lips, going straight for her most sensitive spot. She gasped as her fingers made contact and sent a shock throughout her body.

Alex was no stranger to masturbation, but today was different from the other times. She usually liked to take it slow, gently teasing herself with her fingers as she gradually built up to an intense orgasm. She’d focus on nothing but the act itself, having found that fantasizing about boys only served to kill the mood. But fantasizing about Kara was something else entirely. She’d never felt desire like this before, and she tried not to think about what that might mean.

She was rubbing herself with a speed and hunger she hadn’t thought she was capable of, greedily chasing after that blinding relief. Without her realizing, her other hand had come upwards, pushing up her shirt to grab directly at her breast. In her mind’s eye, she had Kara trapped beneath her, and her hands were roaming to feel everything they could. Alex imagined the sounds Kara would make as she touched her in all the right places.

She was close now, could feel the wave of pleasure cresting right before the break. Her muscles tensed and her toes curled. She sucked in a gasping breath, and then—

“Alex! What’s happening? Are you okay?”

Her eyes shot open, and she found Kara standing over her with panic on her face. Alex was already too far gone, and seeing Kara again in all her naked glory only served to push her further over the edge. Her orgasm rocked her body, sending pleasure radiating out from her core. She couldn’t stop the soft moan that escaped her lips.

Kara looked even more alarmed now. “I’m getting your parents!” she said, turning away.

“No!” Alex’s plea came out as a low groan. Thankfully, Kara seemed to have understood, because she stopped and turned back to Alex.

Neither of them spoke as Alex came down from the high of her orgasm. She was breathing hard. Sweat clung to her brow, its smell mingling with the musky scent of her arousal. She took her hand out of her shorts and pulled down her shirt. She avoided looking at Kara as she grabbed some tissues from her bedside table to wipe her hand clean. She’d never felt more humiliated in her life.

Kara finally broke the silence. “What just happened? Are you okay?”

“I’m fine.” Alex’s cheeks were burning, and she wanted nothing more than to run away from Kara’s concerned questioning. Instead, she took a deep breath, deciding it was best to get it over with. “I was just masturbating.”

“What’s that?”

Right. If she’d known about masturbating, she probably wouldn’t have been so confused. “Do you know what sex is?”

Kara nodded. “Of course! We learned about it in biology class years ago.”

Alex was relieved that she wouldn’t also have to explain about the birds and the bees. “Masturbating is basically like having sex with yourself.”

“Oh.” Kara’s brows wrinkled, like she was thinking that over, and then understanding dawned on her face. “Oh! I thought you were having a seizure or something. It sounded like it hurt, but you were just—”

“Right,” Alex said, cutting her off. “It was just a misunderstanding. So can you go back to bed now?” If she’d thought it was awkward seeing Kara naked before, it was nothing compared to seeing her now, after everything Alex had just done. She just wanted to go to sleep and forget that this whole experience had ever happened.

Kara didn’t move, though. “Can I ask you something, first?”

Alex sighed. “What is it?”

Kara seemed to be having trouble looking Alex in the eye, and there was a slight blush on her cheeks. “How do you masturbate?”

Under normal circumstances, Alex would’ve brushed Kara off and told her to look it up online. But her fantasies from earlier were still fresh in her mind and so, without thinking, she said, “I’ll teach you.”

Kara’s eyes widened. “Really?”

“Yeah, sure,” Alex said with forced casualness. She stopped holding herself back and let her vision travel down Kara’s body. “It’ll be easy since you’re already naked. Just go sit on your bed.”

Kara nodded and did as she was told, and Alex got up and followed after her. Kara looked up at Alex expectantly. “What now?”

“I usually like to start by playing with my boobs, like this.” Alex kneeled down in front of Kara and reached her hand out. She hesitated for just a moment, knowing that it was her last chance to put a stop to this. Instead, she looked Kara in the eye and smiled as she laid her hand on her breast.

“Oh!” Kara jumped at the contact, but she soon relaxed into Alex’s touch.

Alex was teasing Kara’s nipple with her fingers, feeling it stiffen as she circled gently around it. “How’s that feel?”

“Weird… but nice, I think.”

“Good.” Alex’s heart was pounding like she’d just run a marathon, and her fingers burned where they came in contact with Kara’s soft flesh. How could just touching another girl be this exciting? “Try doing the same thing with your other one.”

Without a word, Kara brought her hand to her chest to mimic Alex’s actions. Already, Alex could hear her breathing getting heavier.

“Keep going, just like that,” Alex said. She left Kara’s breast then, and Kara shot her a pleading look that set off a pang in her heart. “Just a second.”

Alex felt like she was suffocating in her clothes, and she tore them off as fast as she could. She was even more turned on than she had thought, if her soaked panties were any indication. When she looked back at Kara, she saw that Kara had stopped playing with herself. Her gaze was fixed on Alex or, more specifically, on the point between her legs.

Alex laughed nervously. “I thought you’d be used to seeing girls naked since you all sleep like this.”

“Sorry!” Kara dropped her eyes to her knees. “I was just surprised. I thought you’d have hair.”

“Oh, that’s alright.” Alex kneeled down again and smiled up at Kara. “I shave it.”

“Why?”

Alex shrugged. “I just like it that way. Lots of people do.”

“Should I shave mine too then?”

“I think yours looks perfect just the way it is.” Feeling bold, Alex ran her fingers through the hair covering Kara’s pussy. “Feels nice, too.”

Kara let out an adorable squeak, and Alex felt her own pussy throb in response.

“Can I keep going?” Alex asked.

Kara nodded, and her hand went back to playing with her breast. She was watching Alex intently.

Alex gently slipped a finger between Kara’s lips. She was happy to feel how quickly it became coated in Kara’s wetness. When she found what she was looking for, Kara stiffened, and Alex heard her take a sharp breath.

Alex remembered then that she was supposed to be teaching Kara. “That was your clit I just touched.” She drew her finger in slow circles around it as she talked. “It’s really sensitive, so you’ll want to pay attention to it while you masturbate.”

Kara was in no position to respond to Alex’s lesson. She threw her head back and squeezed her eyes shut, biting on her lip in a vain attempt to stop a moan from sneaking out.

Alex loved that she was making Kara feel so good. She could tell that Kara was already getting close, but she wasn’t ready to stop just yet. She removed her hand from Kara’s pussy and, before the other girl could complain that she had stopped, she grabbed her hand and guided it downwards. “Your turn to try.”

Kara nodded. Her touch was tentative at first, her fingers exploring somewhere they’d never been before. She rested them on her clit, and, just like Alex had done, started rubbing in circles.

Alex’s breathing was growing heavy just from watching Kara pleasure herself. She reached a hand down to her own aching clit and mirrored the movements Kara was making. She could feel her orgasm building at the thought of Kara's juices on her fingers mixing with her own, and she slowed down her rubbing, not wanting to come right away.

She still couldn’t believe that she was really doing this, watching her new sister rub herself as she did the same. It was so much better than doing it alone, and yet she still wanted more.

With her other hand, she reached forward and once again parted Kara’s lips. Since Kara was taking care of her clit, she traveled lower down the slit, stopping when she found Kara’s entrance. She traced circles around it, gathering up all the wetness she could before she gently pushed past.

Kara gasped, and her pussy tightened around Alex’s finger.

“Keep rubbing,” Alex commanded.

Kara nodded and continued playing with her clit, moaning lightly with each breath.

Alex knew she couldn’t last much longer. She sped up the hand rubbing her own pussy, and at the same time she began plunging her finger in and out of Kara’s. She focused on the sensation of Kara’s pussy gripping her fingers, the smell of their mixed arousal, the sound of their breaths and moans and dripping wetness.

The dam broke, and Alex’s climax rolled over her. At the same time, Kara let out her loudest moan yet, and her pussy began contracting on Alex’s finger. They rode the wave of their orgasms together, and when it was over, they sat basking in the afterglow.

“How was that?” Alex asked after a moment. She slowly removed her finger from Kara and, on impulse, stuck it in her mouth. The taste was better than she had expected, and she wondered if it would be even better getting it straight from the source.

“That was amazing!” Kara said. “I didn’t know it was possible to feel that good.”

Alex smiled. “Good.” Then, she had a sudden realization, and the color drained from her face. “You were really loud though, do you think Mom or Dad heard?”

Kara was silent a moment, seeming to be concentrating on something. “Nope, they still sound like they’re asleep.”

“You can hear them from here?” Alex had almost forgotten that Kara wasn’t human. She’d been distracted by her all-too-human body, after all.

“Yeah, my hearing’s been getting stronger since I got here. It’s how I heard you masturbating, earlier.”

“Well, I’m glad you did,” Alex said with a laugh. “It’s so much better doing it with you.”

“It is?” Kara’s face was red, but there was a smile spreading across it. “Then, can we do it again sometime?”

“’Course we can.” Alex stood up and smiled at Kara. “As your new big sister, it’s my job to make sure you’re happy here.” Before she could rethink it, Alex leaned over and pressed a kiss to Kara’s lips. It was just a quick peck, but it made Alex’s legs wobbly all the same. If the look on Kara’s face was any indication, she felt the same way.

Alex went back to her side of the room. She had decided to forego getting dressed again, having figured that maybe Kryptonians had the right idea there. “Goodnight, Kara.”

“Goodnight, Alex.” There was silence for a while as they got cleaned up and made themselves comfortable in their beds, and then Kara added, “I’m glad you’re my sister.”

“I am too,” Alex said, already drifting off into a blissful sleep.


End file.
